Inhibition of the Acid Corrosion of 10Cr18Ni10Ti and 10Cr18Ni13Mo2Ti Austenitic Steels by Aqueous Extracts of Wood Bark.

The corrosion of 10Cr18Ni10Ti and 10Cr17Ni13Mo2Ti austenitic constructional steels in 5% hydrochloric acid containing an inhibitor based on aqueous extracts of aspen (ABE), spruce (SBE), and pine (PBE) bark was studied by gravimetric and electrochemical methods. Such solutions are used for washing and chemical cleaning of cooking and heat-exchange equipment. The influence of temperature and composition of inhibitors on the process was examined. New data on the kinetics of the acid corrosion of the steels were obtained and analyzed. At equal concentration of 1 g L–1, the inhibiting effect of water-extractable substances (WESs) of wood bark on the acid corrosion of steels increases in the order PBE < SBE < ABE. The inhibiting effect also increases with an increase in the WES concentration to 3.8 g L–1 and in the temperature from 20 to 50°С, on mixing extracts of different kinds of bark, and to a still greater extent on introducing a synergistic agent, hexamethylenetetramine or potassium iodide, into the extracts. [ABSTRACT FROM AUTHOR]